1. Field of the Invention
The present invention relates to a spacer distributing apparatus used in fabricating a liquid crystal display device (hereinafter, as LCD) and particularly, to a distributing apparatus capable of preventing a spacer from being contaminated and adversely affecting the distribution of the spacer.
2. Description of the Related Art
Currently, the range of application of the liquid crystal display device is enlarged due to the rapid development of the liquid crystal display device and the liquid crystal display device is installed in most portable electronic devices due to its light weight. Accordingly, developing the manufacturing technology with a reduced cost and improved productivity is an essential criteria.
Generally, as shown in FIG. 1, a liquid crystal display apparatus includes an upper substrate 30 in which a color filter is formed, a lower substrate 10 in which a thin film transistor array is formed and a liquid crystal layer 22 which is disposed between the two substrates 10 and 30.
On the outer surface of the two substrates 10 and 30, polarizers 11 and 31, for linearly polarizing visible rays, are respectively attached. That is, the polarizer 31 is attached to a surface of the upper substrate 30 and a color filter 32 and a common electrode 33 are formed on the opposite surface where the polarizer is not attached. Also, a polarizer 11 is attached to a surface of the lower substrate 10. On the opposite surface where the polarizer is not attached, a TFT array, including a plurality of gate bus lines 12, a plurality of data bus lines 13, a switching device A, a pixel electrode 16 and the like is formed.
The TFT includes three electrodes including a gate, source and drain, an amorphous-Si for forming a conductive channel which has a current flow between the source electrode and drain electrode caused by an electric field when a positive voltage is applied to the gate electrode, and a passivation layer for protecting the device.
The LCD device with the above composition is formed by attaching the lower substrate which is composed of the TFT and the pixel electrode, and the upper substrate which is a color substrate having a liquid crystal disposed therebetween. An orientation film is formed on opposing surfaces through which the upper and lower substrates face each other, and a sealant is formed on the upper substrate. On the lower substrate, the spacer is formed and then the two substrates are attached.
FIG. 2 is a cross-sectional view showing an LCD device which is formed by attaching an upper substrate and a lower substrate.
On the opposing surfaces of the upper substrate 30 in which the color filter is formed, and a lower substrate 10 in which the TFT array is formed, an alignment layer 36 is printed. Also, the sealant 38 which is printed in a non-active region forms a gap between the two substrates, and prevents leakage of liquid crystal (not shown) which is injected between the two substrates. Also, circular spacer 40 is uniformly distributed between the two substrates so that the two substrates maintain a predetermined interval.
Also, to maintain a proper thickness of the liquid crystal layer in an LCD device, the spacer is distributed to control the gap between the two substrates, and prevent display spots and degradation of visuality, caused by a nonuniformity of the thickness of the liquid crystal layer.
Recently, the LCD device requires a high performance, such as a high contrast ratio, an expansion of the viewing angle field, and a high resolution that enables a uniform display without a display defection over the whole device. To insure high performance of the LCD device, it is necessary to control the interval between the substrates as a predetermined value, and to insure high resolution, it is necessary to control the interval between the substrates to be uniform in the whole device. Therefore, to improve display performance, it is very important that a spacer is uniformly distributed in the whole area of the substrate.
In the LCD device, as the spacer, 10 to 2000 particles having a uniform diameter of from several microns to several tens of microns are uniformly distributed or spread in 1 mm2 as a single step to form an interval, so that the liquid crystal can be injected between the glass substrates or between plastic (organic glass) substrates, or between the plastic substrate and the glass substrate. As the spacer for the liquid crystal, various plastic particles or silica particles can be used.
Generally, as the method for distributing the spacer, there are the wet distribution method and the dry distribution method. The wet distribution method suspends the spacer for the liquid crystal in a solution such as Fron under a colloidal condition and uniformly distributes the resultant product on the substrate in a liquid state. Then, a predetermined amount of spacer is uniformly distributed on the substrate as a single step by vaporizing the solution. However, since the usage of Fron is limited due to environmental problems, the following dry distribution method is commonly used.
The dry distribution method is performed by distributing the spacer without, so-called lumps by charging it positively or negatively. As an example, when a high voltage is generated in an electrode at the end of the nozzle and the air at the circumference thereof is ionized, the spacer carried by the air collides with the negative ions in the air and is negatively ionized. The negatively ionized spacers are led to a substrate on the supporter which is grounded so that they repel each other. The spacers which are negatively ionized on the substrate are positioned at regular intervals by the repulsive force among each other.
FIG. 3 is a view showing an example of a general spacer distributing apparatus.
As shown in the drawing, in the spacer distributing apparatus for a liquid crystal, a stage or table 41 which is grounded, is positioned within the lower portion of a hermetically sealed chamber 40 and a substrate 51 which is a distributed material which is applied to the table is grounded so that the spacer which is a charged fine powder is precisely attached to the grounded substrate 51.
A nozzle unit 42 which freely moves in the left and right directions and front and rear directions on a flat panel is installed at the upper portion of the chamber 40. The nozzle unit 42 is connected to a spacer supply unit 43 by a SUS pipe 44 to discharge the spacer for the liquid crystal. The spacer is carried with an air stream of gas, such as air or nitrogen, from the spacer supply unit 43 to distribute the spacer on the substrate 51.
FIG. 4 is an enlarged view showing the nozzle unit 42. The nozzle unit 42 which is installed at the upper center portion of the chamber 40, includes a nozzle 46 which is composed of a hollow pipe, a supporter 45 for supporting the nozzle 46, a ball bearing 47 which is inserted between the nozzle 46 and supporter 45 so that the nozzle 46 can be freely moved in the left and right directions and front and rear directions, a driving unit (for instance, a motor) for driving the nozzle 46 in the multiplicity of directions, and a cover 49 which covers the nozzle 46.
The cover 49 is attached to prevent the introduction of foreign materials or dust into the inside of the chamber 40 between the nozzle 46 and the supporter 45 when the spacer is distributed to the substrate 51 as the nozzle 46 is moved in the left and right directions and the front and rear directions. The cover 49 is called a dust cover.
However, when the cover 49 is used for a long time, tearing of the cover 49 occurs in the connection between the nozzle 46 and cover 49 due to the frequent movement of the nozzle 46. Therefore, foreign materials can penetrate through the tearing crevice whereby the inside of the chamber 40 becomes polluted.
When the cover 49 becomes torn due to the continuous rotation of the nozzle 46, the spacer which was distributed and lumped in the torn part (A) falls onto the substrate, causing a serious defect in the surface of the LCD.